Our present modern way of life imposes more and more demands on products used for food, feed and pharmaceutical purposes, body care, etc. In this context, there is a continuous need for products which                have reduced calorific values,        have a low fat content,        have an increased fibre content,        have a beneficial effect on intestinal and cutageneous microflora,        have a lower sugar content,        do not cause dental caries,        possess physiologically functional characteristics.        
It is known that various carbohydrates, including fructans such as inulin, can fulfill these demands and can therefore be valuable ingredients for food products, functional food or feed, OTC and pharmaceutical products, cosmetic products etc.
It is known e.g. native inulin can be obtained by industrial methods (F. Perschak, Zükerind.115, (1990), p.466) . Through hot water extraction, an inulin-containing containing extract is separated out from tuber or root cuttings taken from inulin-containing plants. This extract is then demineralised and decolorized. Raftiline® ST is a commercially available product which contains native chicory inulin (Tiense Suikerraffinaderij, Belgium).
These inulin extracts are in fact a mixture of polymer molecules of various chain lengths.
A polydisperse carbohydrate composition such as e.g. inulin can be characterised by the chain length of the individual molecules (the degree of polymerisation or DP), and also by the percentage distribution of the number of molecules of a particular chain length, as well as by the average degree of polymerisation (av. DP).
A native polydisperse composition retains the molecular structure and the polydispersity pattern of the product as separated from its original source.
The degree of polymerisation of native chicory inulin molecules is between 2 and 60, the av. DP is around 11. The percentage distribution of he molecule fractions is approximately 31% for DP 2-9, 24% for DP 10-20, 28% for DP 21-40 and 17% for DP>40 respectively. Native inulin from dahlias with an av. DP of 20 contains a significantly smaller share of oligofructoses and double the quantity of molecules with a chain length of DP>40. Native Jerusalem artichoke inulin on the other hand contains extremely few molecules with DP>40, only about 6%. The oligomer fraction DP<10 accounts for approximately half of the molecules of the native polydisperse inulin of Jerusalem artichoke.
The polydispersity pattern of e.g. fructans strongly depends not only on the original production source from which the fructans are obtained (e.g. in vivo synthesis with plants or microorganisms or in vitro synthesis with enzymes), but also on the point of time at which the polydisperse compositions are extracted (e.g. plant harvest time, the action time of enzymes, etc.). The manner in which the polydisperse compositions are extracted likewise plays a role.
In addition, extracted native polydisperse compositions frequently contain a significant amount of other products such as e.g. monosaccharides and disaccharides such as glucose, fructose and saccharose and impurities such as proteins, salts, colourings, organic acids and technical aids such as solubility affecting products.
State of the Technology
Known products with a changed DP are:                gamma inulin with molecules that have a very specific DP between 50 and 63, as described in WO 87/02679;        inulin I 2255, I 3754 and I 2880 which have an av. DP which is significantly higher than the av. DP of the native inulin from which they are prepared, respectively native chicory, dahlia and Jerusalem artichoke (Sigma, USP.) and which are non-food graded.        fibruline LC (Warcoing, Belgium) a chicory inulin with an av. DP not appreciably higher than native chicory inulin and which contains a significant amount of impurities and low molecular carbohydrates, making its use in many applications impossible.        
A number of processes are known to exist and allow e.g. the production of fractionated inulin with a higher av. DP.
Using alcohol based solvents such as methanol, ethanol or isopropanol, inulin with a higher av. DP can be precipitated and separated by centrifugation. However, this is a fairly complex method. The precipitation is often combined with extremely low temperatures (4° C. and low initial inulin concentration). The alcohol must be removed and the volume that needs to be reconcentrated is large. The yield of this process is extremely low, notwithstanding the fact that a relatively pure end product is obtained.
It is also known that aqueous solutions of inulin can be subjected to crystallisation by the addition of grafting crystals in such a way that the longer chains precipitate and can be separated out by centrifugation.
E. Berghofer (Inulin and Inulin containing crops, Ed. A. Fuchs, Elsevers Sc. Publ., (1993), p 77) describes the isolation of inulin from chicory by means of crystallisation with a slow pattern of cooling (3° C./hour from 95° C. to 4° C.). In this way it is only possible to separate out small amounts of inulin and the product obtained is not sufficiently pure.
It is known (Le Sillon Belge, Apr. 24, 1989) that inulin can be divided into various polymer fractions by applying the technique used in classical industrial physical chemistry, i.e. separation through fractional crystallisation. For this, an inulin solution is gradually cooled using ceiling temperatures between 40° C. and 10° C., where necessary making use of grafting crystals. It is usual for the molecules with a higher DP to precipitate first, followed by the shorter ones, since molecules with a higher DP are less soluble. The isolated fractions then still need to be separated through centrifugation or filtration and washed.
By using enzyme synthesis and a native inulin, or sucrose solution, molecules with a high DP can be obtained (EP 532,775). Though the end product is practically free of oligomers, the remaining sucrose and fructose must be removed using supplementary methods.
As described in EP 627490, it is possible by the use of inulinase to break down the low DP fraction in native inulin. The percentage distribution of the number of molecules with a low DP will be diminished in such a way that the av. DP of the polydisperse end product will increase. The breakdown products glucose and fructose will need to be removed using supplementary methods.
U.S. Pat. No. 4,285,735 describes a preparation process of a dahlia inulin that contains minor amount of inulides, proteins, colours, flavours, external bodies and minerals.
JP-03/280856 describes a production process of an aqueous paste shaped composition comprising β-(2->1) fructan with a degree of polymerisation of 10 to 100. The said fructan is dispersed and present in the paste as a fine granular material.
Aims of the Invention
Notwithstanding the fact that a number of preparation processes of a fractionated fructan composition such as inulin are known, down to the present time there has been no fractionated polydisperse inulin (i.e. inulin with a changed av. DP) available which results in an end product combining four important characteristics in a single product, i.e.                an average DP which is significantly higher than the average DP of native inulin;        an inulin composition which is significantly free of low molecular monosaccharides, dissacharides and oligosaccharides; and        a refined fractionated inulin which is significantly free of impurities such as colourings, salts, proteins and organic acids; and        an end product which is free of technological aids such as solubility affecting products.        
It may on the one hand be necessary to remove monosaccharides and dissacharides and often also oligomer molecules from native polydisperse carbohydrate compositions since these are experienced as hindrances in certain applications. This problem has already been recognised and solved by the present patent application WO 94/12541. Raftiline® LS from Tiense Suikerraffinaderij in Belgium is a product which typically contains no or very few saccharides of a low molecular weight and which is prepared in accordance with WO 94/12541.
On the other hand it can be worthwhile to have available a particular polymer fraction of a polydisperse carbohydrate composition since this may more definitely demonstrate a specific characteristic of the native mixture or because new characteristics can be ascribed to the particular fraction.
The better the fractionation, the purer the end product prepared, the lower the polydispersity and the smaller the standard deviation from the av. DP.
It is therefore still desirable to prepare polydisperse carbohydrate compositions whose DP has been changed in respect to the av. DP of the polydisperse composition that served as starting product. Compositions such as these are referred to below as fractionated carbohydrate polydisperse compositions.
More specifically, the availability of a fractionated inulin composition pure enough to allow the preparation of a high performance inulin would permit many new developments both in the food sector and in other sectors. The availability of pure fractionated inulin also makes possible improvements to the known applications for inulin, if only for the reason that the same characteristics can be achieved using a significantly smaller amount of high performance inulin as compared to native inulin, where the share of low molecular products is decisive. All of which benefits the consumer. The facility of being able to provide inulin in fractions with a specific av. DP would likewise make it possible to develop new applications for inulin.
More generally, there remains the task of finding a new preparation process which allows carbohydrate molecules with a high DP to be fractionated from native polydisperse compositions on the understanding that an endeavour must be made to arrive at an industrially applicable, in other words profitable, methodology, permitting the production of large quantities.
During its research work into pure fractionated polydisperse carbohydrate compositions the applicant chose for crystallisation. Specifically, the known crystallisation methods for inulin were tried out, the aim being to achieve a pure separation of inulin molecules with a high DP. At that point the applicant came up against a filtration problem whenever it wished to use the known processes. When the attempt was made to precipitate chicory inulin according to the state of the art and afterwards to filter it, the filters became clogged, and when centrifugation was tried out, non pure fructans were obtained.
Furthermore the high DP molecule fraction continued to contain a significant amount of glucose, fructose, saccharose and oligomers. It was proved difficult to wash out the filter cake with hot or cold water and to remove these sugars and other non-carbohydrates using a simplified method, i.e. washing.